Electromagnetic fuel injection device for internal combustion engines

ABSTRACT

An electromagnetic fuel injection device for internal combustion engines comprising electric circuit so arranged that the number of cylinders which undergo simultaneous injection in one cycle of the engine is lessened at low rotational speeds where the control time of the amount of fuel injected is relatively long so as to operate all the fuel injection valves through several stages thereby the period of each fuel injection will not correspond to an overlapping period, while for high speed rotation the number of cylinders related to simultaneous injection is increased to equivalently extend said control time.

O United SiiiiGS Patent 1 1 1 1 3,7 24,431

Inoue et al. [451 Apr. 3, 1973 54| ELECTROMAGNETIC FUEL 3,483,85112/196) Rcichardt ..|23 32 EA INJECTION DEVICE FOR INTERNAL 2,992,6407/1961 Knapp ..l23/32 EA 3,181,520 5/1965 .....l23/32 EA COMBUSTIONENGINES 3,521,606 7/1970 .....l23/32 EA [75] lnventors: Takashi Inoue;Takao Masuda; 2,867,200 1/1959 Gryder et al. ..l23l32 EA Takeshi Harada,all of Higashi-Matsuyama, Japan Primary Examiner-Laurence M. Goodridge[73] Assignee: Diesel Kike Kabushiki Kaisha, Au0mey Larson Taylor &Hinds Japan 57 ABSTRACT [22] Flled: July 1970 An electromagnetic fuelinjection device for internal [21] Appl. No.: 54,228 combustion enginescomprising electric circuit so arranged that the number of cylinderswhich undergo simultaneous injection in one cycle of the engine is 2% y''g 123/119 39 1 23 lessened at low rotational speeds where the control d32 H 9 time of the amount of fuel injected is relatively long so 1 0 canl 139 5 as to operate all the fuel injection valves through severalstages thereby the period of each fuel injection will not correspond toan overlapping period, while for [56] References cued high speedrotation the number of cylinders related to UNITED STATES PATENTSsimultaneous injection is increased to equivalently extend said controltime. 3,522,794 8/1970 Reichardt ..l23/32 EA 3,587,536 6/1971 lnoue etal. ..l23/32 EA 4 Claims, 7 Drawing Figures NO N PATENTEDAPR 3 1975SHEET 1 BF {1 PATENTEDAPR3 1975 3,724,431

SHEET 2 [IF 4 PATENTED APR 3 1975 SHEET 3 BF 4 PATENTEDAPR3 19753,724,431

I SHEET u m 4 FIG.6

INVENTOR ATTORNEY ELECTROMAGNETIC FUEL INJECTION DEVICE FOR INTERNALCOMBUSTION ENGINES This invention relates to an electromagnetic fuelinjection device for multi-cylinder type internal combustion engines.

Heretofore, a fuel injection device of this type pro vided controlledfuel injection in an amount in accordance with the duration T of thevoltage applied to an electromagnetic fuel injection valve. With therise of engine rotation speed N, the controllable time of the engine I(t (60/N sec) will be decreased. When the controllable time is reducedto a value smaller than the duration T of the voltage applied to theelectromagnetic valve, control of the amount of fuel injected has beenimpossible. It is also known in the prior art that an engine equippedwith this sort of device is constructed to perform all cylindersimultaneous fuel injection for each cylinder of four cyclemulti-cylinder engine and that during the injection period in certaincylinders suction valves thereof are opened while their exhaust valvesare insufficiently closed (valve overlap) so that the gas mixture isblown offwastefully. This effect was particularly apparent at the lowspeed rotation consequent on the bad fuel consumption rate. The presentinvention provides an electromagnetic fuel injection system for aninternal combustion engine comprising a rotational speed to voltageconverter circuit for producing voltage output pulses in accordance withthe rotational speed of the engine, a mono-stable multivibrator circuitfor receiving the pulses produced by the converter and producing anoutput in accordance therewith and a control circuit for controllingenergization of a plurality of sets of controlcoils to thereby controlactuation of a corresponding plurality of fuel injection valves. At lowspeed operation, the outputs of the multivibrator circuit and converterare connected to the control circuit so as to provide alternateenergization of the sets of control coils and hence provide simultaneousminority-cylinder injection. A speed responsive switch suppresses theoutput pulses from the converter when the engines reaches apredetermined speed so as to provide simultaneous energization of thesets of coils and hence provides simultaneous majoritycylinderinjection.

In order that the invention may be more clearly understood, referencewill now be made to the accompanying drawings in which:

FIG. 1 is a graph showing the fuel requirement characteristics as afunction of rotation speed of an internal combustion engine;

FIG. 2 is a block diagram showing a fuel injection device according tothe invention;

F IG. 3 is an electrical circuit diagram of the fuel injection device;

FIG. 4 is a diagram showing pulse waveforms of potentials at variousjunctions of an injection amount correcting circuit;

FIGS. 5 and 6 are diagrams showing pulse waveforms at each part of thecircuit, in each of which (i) represents a set of waveforms relating tosimultaneous fuel injection for two cylinders, and (ii) represents a setof waveforms relating to simultaneous fuel injection for four cylinders;and

FIG. 7 is a graph showing a modification of the characteristics of theduration T of pulse.

Referring now to the schematic block diagram of FIG. 2, block A denotesa known rotation speed-voltage converting circuit for producing avoltage pulse related to the rotation speed of the engine. Block Bdenotes a known monostable multivibrator circuit which generates arectangular pulse whose frequency varies with the rotation speed of theengine and whose pulse length changes with variations in the vacuum ofthe suction pipe of the engine. Block D designates an output amplifiercircuit for controlling the fuel injec tion valves of the engine E.Block C designates an injection amount correcting circuit which correctsthe fuel injection amount relative to the rotation speed of engine. Theconstruction of these circuits is now shown in particulars in FIG. 3. Inthe figure, section A includes intermittent contacts S1, S2 of theengine, capacitors C1, C2, etc, and generates two pulse trainsalternately produced by frequencies proportioned to the engine speedthrough alternate closing of the contacts S1 and S2. Section B includesa multivibrator circuit having transistors Trl and Tr2, and a timingelement having transformer L and resistors R0 and R1. The iron core oftransformer L moves in proportion to the vacuum of a suction pipe P ofthe engine and can change the inductance of a secondary coil of thetransformer L so that the duration of the pulses produced varies withthe variation in the vacuum of the suction pipe of the engine. Section Cis formed of transistors Tr3 Tr7, capacitor C3 C7, resistors R3 R5,variable resistors VRl VR6, diodes D1 D3 and a rotation responsiveswitch S3, and is arranged to satisfy characteristics of fuelrequirements. Section D is formed of transistors Tr8 Trll, control coilsLl L4 of electromagnetic fuel injection valves divided into two groupseach consisting of two coils and diodes D4 and D5.

Application of the device of the invention to a four cylinder engine isnow illustrated in detail. In reference to FIG. 3, the rotationresponsive switch S3 is opened during the low speed rotation (3,500r.p.m. or less in an experimental engine). The base of the transistorTr8 becomes negative only when the intermittent contact S1 of therotation speed-voltage converter circuit is closed. The contact W of themonostable multivibrator circuit B is supplied with a negative triggerpulse through the circuit of the capacitor C1 and diode.

Accordingly, the base of transistor Trl becomes negative andnon-conductive and the transistor Tr2 conductive. Current flows in theprimary coil of the transformer L and a voltage is induced in thesecondary coil. In consequence, current produced by the induced voltageflows in the resistor R1 causing a drop in the terminal voltage of theresistor R1 generated from a power source voltage and turns the base ofthe transistor Trl negative. The current of the induced voltage isexponentially reduced but it still maintains the base of the transistorTrl negative until the current drops below a predetermined value.Therefore, the transistor Tr2 is retained in conductive state andgenerates on a junction U1 a pulse T0 related to the induced voltage ofthe transformer L. In FIG. 4, the pulse T0 is shown at waveform U1. Inthe same figure, the ordinate denotes the amplitude and the abscissadenotes the time t.

Hence, the bases of the transistors Tr8 and Trll connected to theterminal U1 becomes negative through the pulse TO. As the intermittentcontact S2 is opened the base of the transistor T11 is retained inpositive. The base of the transistor Tr8 turns negative andnonconducting and the transistor Tr9 becomes conducting. Theelectromagnetic coils of the fuel injection valves L1 and L2 are excitedand fuel is injected. On the other hand, the base of the transistor Trl1 is fed positive and negative pulses so that the base thereof becomesconducting.

Thus, the transistor TrlI) turns non-conducting. Therefore, the fuelinjection valves L3 and L4 will not inject fuel. When the intermittentcontact S1 is opened and the contact S2 is closed, then the triggerpulse passing through the capacitor C2 and diode is fed to a junction W.Said pulse generates the pulse T thereby providing anegative pulse tothe bases of transistors Tr9 and Trll. As the contact S1 is opened thebase of transistor Tr8 turns positive and the transistor Tr9 turnsnon-conducting. Therefore, the valves L1 and L2 will not inject fuel butthe valves L3 and L4 will inject fuel. Accordingly, at a low speedrotation of the engine, each of the two cylinders undergo simultaneousinjection alternately (hereinafter referred to as simultaneous injectionfor two cylinders).

In the subsequent high speed rotation of the engine, the rotationresponsive switch S3 is closed so that a positive pulse is supplied viaintermittent contacts S1 and S2 to the fuel injection valves Ll-L4 andshortcircuited through diodes D4 and D5. At the same time, the pulsefrom the intermittent contact S2 passing through the capacitor C2 willdisappear. The pulse T0 is generated only through the intermittentcontact S1. Hence, assuming that the period of the pulse T0 is t beforeshortcircuiting of S3 this period becomes 2: after shortcircuiting. Thusthe fuel injection valves Ll-L4 will make simultaneous injection by thepulse T0 (hereinafter referred to as simultaneous injection in fourcylinders). This is shown in FIG. 5, in which the ordinate denotes thepulse and the absicissa denotes the time, (i) shows simultaneousinjection in two cylinders, and (ii) simultaneous injection in fourcylinders. According to the invention, therefore, each two cylindersalternately undergo fuel injection at the low speed of the engine andeach four cylinders simultaneous injection at the high speed of theengine. Furthermore, the period at the time of the four cylindersimultaneous injection is double the period of two cylinder simultaneousinjection. There is caused no variation in the injection amount of fuelbefore and after switching over of the injection.

In accordance with the present invention, moreover, the correction ofthe fuel injection amount responsive to the engine r.p.m. is effectivelyperformed. Generally, the air suction amount of the internal combustionengine initially increases with the rise of rotation speed due toresistance of the suction air pipe etc. and subsequently it decreases ashas been well known. Thus it is required to vary the amount of fuelsupply in conformity with this circumstance. The relation of the fuelsupply and the rotation speed of engine is shown in FIG. 1, in which theordinate shows an injection amount of and the abscissa shows therotation speed N of the engine. The correction of the fuel injectionamount is realized in the circuit of section C. The pulse T0 generatedin the collector of the transistor Tr2 of circuit B is also supplied tothe fuel injection amount correcting circuit C. The transistor Tr3produces on junction U2 a pulse Tl which is shown in FIG. 4 at waveformU2 as and is determined by the capacitor C3.

and the resistor R3. The transistor Tr4 produces on junction U3 a pulseT2 which is shown in FIG. 4 at waveform U3 and is determined by thecapacitor C4 and the variable resistors VRl and VR2.

The transistor Tr5 produces on junction U4 a pulse T3 which is shown atwaveform U4 in FIG. 4 and is determined by the capacitor C5 and thevariable resistors VR3,VR4. The transistor Tr6 produces on point US apulse T4 which is shown in FIG. 4 at waveform US in an inverted form ofthe pulse T3. Under this condition, the transistor Tr6 is in conductingstate so that the capacitor C6 is discharged with the dischargecharacteristics as determined by the variable resistor VRS. When thepulse T4 disappears then the transistor Tr6 becomes non-conducting andthe capacitor C7 is charged. The charging process is performed with thecharacteristics as determined by the variable resistor VR6. The pulse ofthe transistor T2 is applied in the charge through the diode D3 to makeconstant the initial condition of the discharge potential. Accordingly,the potential of the connection U6 will vary as shown in FIG. 4 atwaveform U6. In FIG. 4, the portion or part a of the waveform U6designates the discharge process of the capacitor C6 and the portion orpart B denotes the charge process thereof. This potential is amplifiedby the transistor Tr7 and the amplified potential is supplied to ajunction U7 of secondary coil of the transformer L through the variableresistor VR7.

If the potential is high in the junction U7 the time is shortened toretain the point W in the negative by the transformer L. The pulselength of the pulse T0 will then become small, and if the potential islow the pulse length of the pulse T0 becomes large. As the rotationspeed of the engine is raised the pulses T0-T4 move to v the left asshown by dotted lines in FIG. 4. As the potential of the junction U7will vary as shown in the dotted waveform since the pulse T2 is appliedtherein earlier. This pulse T2 is supplied at point Z, corresponding tothe engine r.p.m. No of FIG. 1, from part B of the low speed rotationarea with the rise of speed and applied in part a in the high speedrotation area. Thus, the potential of the junction U7 decreases byincrease of rotation speed at the low speed rotation side and increasesat the high speed rotation side with Z as a turning point as shown inFIG. 4. As the result, a voltage characteristic of a chevron-shape maybe obtained as shown in FIG. 1.

As hereinbefore described, the injection period in the four cylindersimultaneous injection is double the period of the two cylindersimultaneous injection. If the charge and discharge circuit includingthe capacitor C6 in the four cylinder simultaneous injection is same asin the two cylinder simultaneous injection, the position of point Zcorresponding to the engine rotation speed No will be displaced. Sinceit is provided that the injection period is doubled, or the timeabscissa is double the previous length, the time constant of the chargeand discharge circuit is required to be doubled. This adjustment may beperformed in the following way. Simultaneously as the switch S3 isclosed in response to the high speed rotation of the engine the negativesides of longer and the pulse length of the pulses T2, T3 is doui bled.As the capacitor C7, which was formerly open circuited, is connectedv inparallel with the capacitor C6, and assuming that the capacitance of thecapacitor C6 is equal to that of the capacitor C7, then the gradients ofthe portions a and ,8 of the waveform U6 of FIG. 4 are respectivelyturned to half due to the consequent change in rise time. In FIG. 6,curves Ul-U7 respectively represent voltage waveforms at variousjunctions, the ordinate denoting an amplitude and the abscissa denotingtime. In the same figure, (i) shows simultaneous injection for twocylinders and (ii) simultaneous injection for four cylinders. As will beapparent from this figure, the period of each pulse in case (ii) isdouble that of each pulse of (i). The potentials X3 Z0: of the waveformU7 will have a gradient of characteristics as in XlBlZlal. Thus thepotential e at the termination of second pulse T0 affecting themultivibrator circuit B is common to both cases (i) and (ii). Eventhough the potential is changed over the pulse length of the secondpulse T0 is not changed and accordingly the injection characteristicswill not become non-continuous. Comparison of the potential e must beattempted at the high speed rotation side but now it has been made atthe low speed rotation side for convenience of description.

Characteristics of the continued time T of applied voltage may bemodified, as shown at dotted line a in FIG. 7, by adjusting the variableresistors VRl-VR4 to desirably define the pulse lengths of the pulsesT2, T3, and adjusting the variable resistors VRS, VR6 to change thedischarge time of the capacitor C6 and the curve XBYZoz of the waveformsU6, U7 shown in FIG. 4.

It is apparent that another transistor circuit for generating pulses T5,T6 may be provided between the pulses T3 and T4 with the pulses T3 andT6 applied to the base of the added transistor to form an OR-circuit andchange the discharge waveform of the capacitor thereby providingirregular characteristics thereto as shown in dotted curve b of FIG. 7.Change of the rotation speed of engine may be obtained by changing theturn of the throttle valve by the accelerator pedal to change the vacuumof the suction air pipe P, the induced voltage of the transformer Lresponsive to the vacuum, and the pulse length of the pulse TO, therebyadjusting the injection amount.

In accordance with, the invention, as described above, the device may beswitched over to the four cylinder simultaneous injection at the highspeed rotation of the engine at which the fuel injection amount may befairly controlled. At the same time, the device will be switched over tothe four cylinder injection and thereby period of injection may bedoubled. As the result, there will not be produced any difference in theinjection amount of fuel before and after switchover from the twocylinder to the four cylinder operation. The fuel amount adjusting meansmay have a characteristic as desired adapted for the engine so as toelevate the consumption of fuel. The duration of the pulse in theswitchover operation will not have discontinuity so that stable controlmay be obtained over the whole area of rotation speed of the engine.

It is of course to be noted that the switchover operation is not limitedonly to the two-to-four cylinder fuel injection but it may also beapplied to the fuel injection in the ratio of 1:2.

While the invention has been described in detail with respect to aparticular preferred embodiment of the invention it will be understoodthat various changes and modifications may be made without departingfrom the spirit and scope of the invention.

What is claimed is:

1. An electromagnetic fuel injection system for an internal combustionengine, comprising rotational speed to voltage converter means forproducing voltage output pulses in accordance with the rotational speedof the engine, monostable multivibrator circuit means for receiving saidpulses and producing an output in accordance therewith, control circuitmeans for controlling energization of a plurality of sets of controlcoils for controlling actuation of a corresponding plurality of fuelinjection valves, means for connecting the output of said convertermeans and the output of said multivibrator circuit means to the input ofsaid control circuit means so as to provide alternate energization of atleast two sets of said sets of control coils and hence providesimultaneous minority-cylinder injection, and speed responsive switchingmeans for suppressing output pulses from said converter means when theengine reaches a predetermined speed so as to provide simultaneousenergization of said at least two sets of coils and hence providesimultaneous majority-cylinder injection, said system further comprisingtiming circuit means connected to the input of said control circuitmeans for controlling the fuel injection control voltage in accordancewith the fuel supply versus rotational speed characteristic of theengine, said timing circuit including a discharge circuit and said speedresponsive switching means including means for varying the dischargetime of said discharge circuit when the engine reaches saidpredetermined speed, said timing circuit including a plurality of RCcomponents for determining the time constant of said timing circuit andsaid speed responsive switching means including a switch means forswitching selective ones of said RC components in and out of said timingcircuit to control charging and discharging of said timing circuit so asto maintain the rotational speed-fuel injection characteristic of thesystem.

2. A system as claimed in claim 1 wherein the time constant of saidtiming circuit is doubled when the system switches from simultaneousminority-cylinder injection to simultaneous majority-cylinder injection.

3. A system as claimed in claim 1 wherein said control circuit meansincludes at least first and second switching transistors for controllingenergization of said coils and said means for connecting the output ofsaid converter means to said control circuit means comprises alternatelyoperable switches for controlling the period during which saidtransistors conduct, said speed responsive switching means including aswitch for, when actuated, substantially short-circuiting one of saidalternately operable switches to thereby increase the period duringwhich at least one of said first and second switching transistorsconducts.

4. A system as claimed in claim 1 wherein said monostable multivibratorcircuit means includes means for varying the duration of the outputpulses produced 5 thereby in accordance with the suction forces exertedby the engine suction pipe.

1. An electromagnetic fuel injection system for an internal combustionengine, comprising rotational speed to voltage converter means forproducing voltage output pulses in accordance with the rotational speedof the engine, monostable multivibrator circuit means for receiving saidpulses and producing an output in accordance therewith, control circuitmeans for controlling energization of a plurality of sets of controlcoils for controlling actuAtion of a corresponding plurality of fuelinjection valves, means for connecting the output of said convertermeans and the output of said multivibrator circuit means to the input ofsaid control circuit means so as to provide alternate energization of atleast two sets of said sets of control coils and hence providesimultaneous minority-cylinder injection, and speed responsive switchingmeans for suppressing output pulses from said converter means when theengine reaches a predetermined speed so as to provide simultaneousenergization of said at least two sets of coils and hence providesimultaneous majority-cylinder injection, said system further comprisingtiming circuit means connected to the input of said control circuitmeans for controlling the fuel injection control voltage in accordancewith the fuel supply versus rotational speed characteristic of theengine, said timing circuit including a discharge circuit and said speedresponsive switching means including means for varying the dischargetime of said discharge circuit when the engine reaches saidpredetermined speed, said timing circuit including a plurality of RCcomponents for determining the time constant of said timing circuit andsaid speed responsive switching means including a switch means forswitching selective ones of said RC components in and out of said timingcircuit to control charging and discharging of said timing circuit so asto maintain the rotational speed-fuel injection characteristic of thesystem.
 2. A system as claimed in claim 1 wherein the time constant ofsaid timing circuit is doubled when the system switches fromsimultaneous minority-cylinder injection to simultaneousmajority-cylinder injection.
 3. A system as claimed in claim 1 whereinsaid control circuit means includes at least first and second switchingtransistors for controlling energization of said coils and said meansfor connecting the output of said converter means to said controlcircuit means comprises alternately operable switches for controllingthe period during which said transistors conduct, said speed responsiveswitching means including a switch for, when actuated, substantiallyshort-circuiting one of said alternately operable switches to therebyincrease the period during which at least one of said first and secondswitching transistors conducts.
 4. A system as claimed in claim 1wherein said monostable multivibrator circuit means includes means forvarying the duration of the output pulses produced thereby in accordancewith the suction forces exerted by the engine suction pipe.